[英]Do I need to call NotifyPropertyChange() in code-behind?
在我的程序中,我想在我的其他contentPresenter
获得焦点时禁用contentPresenter
。 每个演示者都由位于我的MainWindowViewModel
的属性表示。 这也是两个演示者的IsEnabled
属性所在的位置。
两个contentPresenters
都使用以下结构创建:UserControl - > ViewModel - > Data Model。
现在我试图通过从获得焦点的contentPresenter
的代码隐藏更改主窗口的ViewModel中的IsEnabled
属性来禁用必要的contentPresenter
。
contentPresenter
用户控件代码隐藏:
public partial class EditBlockUC : UserControl
{
public EditBlockViewModel ViewModel { get { return DataContext as EditBlockViewModel; } }
public EditBlockUC()
{
InitializeComponent();
}
//Runs when the user control gets focus
private void UserControl_GotFocus(object sender, RoutedEventArgs e)
{
//This UserControl has access to MainWindowViewModel through
//it's own ViewModel, EditBlockViewModel
ViewModel.MainViewModel.LeftWidgetEnabled = false;
}
}
该行: ViewModel.MainViewModel.LeftWidgetEnabled = false;
在主窗口的视图模型中成功更改属性,但视图不受影响。 我可以通过找到一种方法调用NotifyPropertyChange()
来解决这个问题吗? 如果是这样,我该怎么做?
如果这是完全错误的解决方案,请告诉我,并帮我修复它。
谢谢
更新1:
我完整的基类:
public class PropertyChangedBase : INotifyPropertyChanged
{
public event PropertyChangedEventHandler PropertyChanged;
protected virtual void OnPropertyChanged(string propertyName)
{
PropertyChangedEventHandler handler = PropertyChanged;
if (handler != null) handler(this, new PropertyChangedEventArgs(propertyName));
}
public virtual void NotifyPropertyChange<TProperty>(Expression<Func<TProperty>> property)
{
var lambda = (LambdaExpression)property;
MemberExpression memberExpression;
if (lambda.Body is UnaryExpression)
{
var unaryExpression = (UnaryExpression)lambda.Body;
memberExpression = (MemberExpression)unaryExpression.Operand;
}
else
memberExpression = (MemberExpression)lambda.Body;
OnPropertyChanged(memberExpression.Member.Name);
}
protected bool SetField<T>(ref T field, T value, string propertyName)
{
if (EqualityComparer<T>.Default.Equals(field, value)) return false;
field = value;
OnPropertyChanged(propertyName);
return true;
}
}
更新2:
我的LeftWidgetEnabled
属性:
public bool LeftWidgetEnabled
{
get { return _leftWidgetEnabled; }
set { SetField(ref _leftWidgetEnabled, value, "LeftWidgetEnabled"); }
}
ViewModel.MainViewModel
类的LeftWidgetEnabled
必须如下所示:
private bool leftWidgetEnabled;
public bool LeftWidgetEnabled
{
get { return leftWidgetEnabled; }
set { SetField(ref leftWidgetEnabled, value, "LeftWidgetEnabled"); }
}
此外,您的MainViewModel
必须实现INotifyPropertyChanged 。
你最好让MainViewModel
从ViewModelBase
继承,让ViewModelBase
实现INotifyPropertyChanged 。
public class MainViewModel : ViewModelBase
{
private bool leftWidgetEnabled;
public bool LeftWidgetEnabled
{
get { return leftWidgetEnabled; }
set { SetField(ref leftWidgetEnabled, value, "LeftWidgetEnabled"); }
}
}
public class ViewModelBase : INotifyPropertyChanged
{
// boiler-plate
public event PropertyChangedEventHandler PropertyChanged;
protected virtual void OnPropertyChanged(string propertyName)
{
PropertyChangedEventHandler handler = PropertyChanged;
if (handler != null) handler(this, new PropertyChangedEventArgs(propertyName));
}
protected bool SetField<T>(ref T field, T value, string propertyName)
{
if (EqualityComparer<T>.Default.Equals(field, value)) return false;
field = value;
OnPropertyChanged(propertyName);
return true;
}
}
更新1
然后,您的ContentPresenter应绑定如下:
<ContentPresenter IsEnabled="{Binding Path=LeftWidgetEnabled}" />
而UserControl
的DataContext
( ContentPresenter
所在的位置)应该是MainViewModel
一个实例。
例如:
<UserControl
x:Class="MyApplication.UserControl1"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
xmlns:viewModels="**PATH TO YOUR VIEWMODELS-ASSEMBLY**"
mc:Ignorable="d">
<UserControl.DataContext>
<viewModels:MainViewModel />
</UserControl.DataContext>
<ContentPresenter IsEnabled="{Binding Path=LeftWidgetEnabled}" />
</UserControl>
您实现INotifyPropertyChanged如下所示
class ViewModel : INotifyPropertyChanged
{
private bool leftWidgetEnabled;
public bool LeftWidgetEnabled
{
get
{
return leftWidgetEnabled;
}
set
{
leftWidgetEnabled=value
OnPropertyChanged("LeftWidgetEnabled");
}
}
public void OnPropertyChanged(string PropertyName)
{
if (PropertyChanged != null)
{
PropertyChanged(this, new PropertyChangedEventArgs(PropertyName));
}
}
public event PropertyChangedEventHandler PropertyChanged;
}
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